1. Field of the Invention
The present invention relates to a color liquid crystal display apparatus and a method for driving the same, in which a desired color image, owing to birefringence of liquid crystal, can be displayed stably without deviation of a displayed color due to a change in environment temperature or source voltage or the like.
2. Description of the Related Art
A color liquid crystal display apparatus of an ECB (electrically controlled birefringence) system is conventionally known. In the ECB system, an electric field is applied to liquid crystal, thereby changing the arrangement of molecules of liquid crystal, and a color image is displayed utilizing the change in birefringence of the liquid crystal due to the change of the molecular arrangement. This type of color liquid crystal display apparatus is suitable for a portable device, since it does not require a back light and consumes less power. However, it is disadvantageous in that so-called color deviation easily occurs, i.e., a displayed color is likely to change depending on a change in environment temperature and/or source voltage.
FIG. 1 is a graph showing the relationship between an applied voltage and a displayed color at different temperatures in a color liquid crystal display apparatus of the EBC system. In FIG. 1, the abscissa represents the applied voltage and the ordinate represents the change in color. The solid line represents the change in color at 25.degree. C., the dot line represents the change in color at 40.degree. C. and the one-dot-chain line represents the same at 0.degree. C.
As shown in the graph, in the conventional color liquid crystal display, the displayed color changes in accordance with the environment temperature, i.e., the temperature of a liquid crystal display, even when the same voltage is applied. Therefore, a stable color image cannot be displayed. In addition, the displayed color is varied in different voltages (VG, VG').
Further, when a circuit for generating a voltage to be applied to electrodes of a liquid crystal element is of a type in which a source voltage supplied from a power source (e.g., a battery) is divided or boosted before it is applied to the electrodes, the voltage applied to the electrodes is varied in accordance with change in the source voltage due to, for example, consumption of the battery. For this reason, an effective voltage applied to the liquid crystal is varied, with the result that the color corresponding to image data cannot be displayed, that is, the color deviation occurs.